Power electronics components, such as single power electronics components or power electronic modules, are commonly used in high powered devices for switching high currents and operating on high voltages. With single power electronics components reference is made to high power thyristors and diodes, for example. Power electronics modules contain multiple of switch components which are situated in a same component housing and typically internally connected to each other to provide a certain circuit structure.
Power electronics modules are used, for example, for producing certain power conversion circuits, such as inverters and converters. An example of a power electronics module contains two IGBTs (Insulated Gate Bi-polar Transistors) which are connected in series inside the module. Other examples may include bridge topologies or parts of bridge topologies which are readily electrically connected inside the module.
Power electronics modules or single power electronics components may also comprise a base plate which is typically made of copper. The purpose of the base plate is to conduct the heat generated by the semiconductors to a cooling device, such as heatsink. The surface of the base plate is typically a substantially planar surface to which a heatsink can be attached. The heatsink is further dimensioned to take into account the amount of heat generated by the semiconductor components in the module.
FIG. 1 shows an example of a cross-section of a power electronics module 1 attached to a heatsink 2. The power electronics module of the example comprises two semiconductor chips 11, 12 which are soldered to a direct copper bonding (DCB) structure. The DCB structure of the example has two copper plates 3 and a ceramic layer 4 between the copper plates 3. The DCB structure is soldered with a solder layer 5 on the top of a copper base plate 7 of the module. The module further comprises a housing 6 which is shown with a dash-dot line surrounding the DCB structure and the chips.
The module of the example of FIG. 1 is attached to a heatsink such that a thermal interface material 8 is positioned between the base plate of the module and the base plate of the heatsink. The purpose of the thermal interface material is to transfer the heat from the module's base plate to the heatsink as effectively as possible. It should be noted that FIG. 1 is provided only to show an example of structure of power electronic module attached to a heatsink. It is clear that other kinds of structures exist.
Power electronics module's internal electronics packing density increases gradually with advanced construction materials and manufacturing methods. This is leading to more challenging module external cooling solutions as devices are able to create very high, over 35 W/cm2, hot spots to the heatsink surface.
In view of cooling the situation is most demanding when the module is operated at its maximum current and voltage level i.e. at maximum power. In this condition the conventional aluminium heat sinks' baseplate spreading thermal resistance is too high for the module base plate high heat spots. That is, a conventional aluminium heatsink is not able to spread the heat transferred from the baseplate of the module fast enough. This results in both higher heatsink-to-baseplate temperatures and chip-to-junction temperatures accordingly. Although novel components may allow higher junction temperatures than before due to novel chip material, the component may not be fully utilized unless the power electronics module's external cooling in not at appropriate level.
Common power electronics module external cooling solutions include for example aluminium heat sinks. These conventional solutions are quite sufficient for base plate heat loss densities of typical power electronics modules.
More demanding applications with higher base plate heat loss densities, e.g. over 35 W/cm2, require clearly more effective heat transfer from the base plate. Typically heat transfer is increased for example by increasing cooling air flow rate with larger cooling fans, modifying the aluminium heat sink in different ways like. Modification may include adding a copper heat spreading plate in to the base plate or replacing the heatsink aluminium cooling fins with copper fins. More effective cooling arrangements can be obtained by replacing the aluminium heat sink with heat pipe heat sinks or thermosiphon cooling devices.
Common challenge for these more efficient heat sink and cooling designs is that their cost is significantly higher than conventional aluminium heat sink's. The cost increase derives from several issues like more laborious manufacturing, more complex manufacturing, and higher price materials. It would thus be beneficial to manage the centralized heat loss density within the power electronics module and this way enable use of relatively low cost heat sink solutions.